1. Technical Field
The present invention relates to a quantum interference device, an atomic oscillator, and a moving object.
2. Related Art
An atomic oscillator that oscillates based on the energy transition of atoms of alkali metal, such as rubidium and cesium, is known. In general, the operating principle of the atomic oscillator is largely divided into a method using a double resonance phenomenon caused by light and a microwave and a method using coherent population trapping (CPT) caused by two types of light components having different wavelengths.
In the atomic oscillator of any method, in order to seal alkali metal in a gas cell together with buffer gas and keep the alkali metal in a gas state, it is necessary to heat the gas cell to a predetermined temperature. In addition, excitation light for exciting the alkali metal is emitted into the gas cell, and the intensity of the excitation light transmitted through the gas cell is detected.
In general, in the gas cell, all of the alkali metal is not gasified, but a part of the alkali metal is present as liquid as a surplus. The surplus alkali metal is liquefied by being deposited (condensed) on a low-temperature portion of the gas cell.
When such surplus alkali metal atoms are present in the excitation light passage area, the alkali metal atoms block the excitation light. As a result, the oscillation characteristics of the atomic oscillator are degraded.
Therefore, for example, in an atomic oscillator disclosed in JP-A-2009-302706, a plurality of heaters are disposed on each of the excitation light incidence surface and the excitation light emission surface of the gas cell in which gaseous metal atoms are sealed.
In the atomic oscillator disclosed in JP-A-2009-302706, however, since the heaters are disposed next to the gas cell, there has been a problem in that an unnecessary magnetic field generated in the heaters by current application acts on the alkali metal in the gas cell and this degrades the oscillation characteristics. In particular, when a plurality of heaters are provided, if the amount of current application to each heater is changed to keep the temperature in the gas cell constant, the above-problem becomes noticeable since not only the magnitude but also the direction of the unnecessary magnetic field is changed.
In addition, in the atomic oscillator disclosed in JP-A-2009-302706, since a plurality of heaters are provided, for example, the number of wiring lines to the heaters is increased. As a result, there has also been a problem in that the entire atomic oscillator becomes large.